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Modeling and implementation of tandem polymer solar cells using wide‐bandgap front cells
摘要： Tandem device architectures offer a route to greatly increase the maximum possible power conversion efficiencies (PCEs) of polymer solar cells, however, the complexity of tandem cell device fabrication (such as selecting bandgaps of the front and back cells, current matching, thickness, and recombination layer optimization) often result in lower PCEs than are observed in single‐junction devices. In this study, we analyze the influence of front cell and back cell bandgaps and use transfer matrix modeling to rationally design and optimize effective tandem solar cell structures before actual device fabrication. Our approach allows us to estimate tandem device parameters based on known absorption coefficients and open‐circuit voltages of different active layer materials and design devices without wasting valuable time and materials. Using this approach, we have investigated a series of wide bandgap, high voltage photovoltaic polymers as front cells in tandem devices with PTB7‐Th as a back cell. In this way, we have been able to demonstrate tandem devices with PCE of up to 12.8% with minimal consumption of valuable photoactive materials in tandem device optimization. This value represents one of the highest PCE values to date for fullerene‐based tandem solar cells.
关键词： tandem solar cells,polymer solar cells,solar cells
更新于2025-09-12 10:27:22
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Flexible ITO-free sky-blue polymer light-emitting diodes and printed polymer solar cells based on AgNW/PI transparent conductive electrode
摘要： In this work, transparent and conductive as well as flexible silver nanowire/polyimide (AgNW/PI) composite film with an average figure of merit as high as 111.3, which is the ratio of electronic conductivity to optical conductivity, is produced by a simple peel-off method without any post treatments. When employing the AgNW/PI composite film as the flexible transparent conductive anode in blue polymer light-emitting diodes (PLEDs), the device shows a high external quantum efficiency of 3.42% which is comparable to the rigid ITO-based control device with an efficiency of 3.96%. Moreover, for the flexible printed polymer solar cell (PSCs) with AgNW/PI as the transparent conductive anode, a high power conversion efficiency of 4.01% is achieved, which is also comparable to that of the rigid ITO-based PSC. This work systematically demonstrates that AgNW/PI composite film has a promising prospect for application in all kinds of flexible optoelectronic devices, such as light-emitting diodes, solar cells, flat panel displays, and so on.
关键词： Printing,ITO-free,Flexible Ag nanowire/polyimide,Polymer solar cells,Polymer light-emitting diodes
更新于2025-09-12 10:27:22
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Understanding of Imine Substitution in Wide Bandgap Polymer Donor–Induced Efficiency Enhancement in All-Polymer Solar Cells
摘要： All-polymer solar cells (all-PSCs) are proven to possess outstanding thermal and mechanical stabilities. However, concurrently achieving appropriate phase-separated pattern, efficient charge transportation, and adequate charge transfer between donor and acceptor components is still a challenge, and thus, only a few polymer-polymer BHJ blends have yielded BHJ device PCEs >8%. Generally, polymer backbone substitutions may have a direct influence on the device performance. Thus, this report examines a set of wide bandgap polymer donor analogues composed of thienothiophene (TT) or thiazolothiazole (TTz) motif, and their all-PSC device performance with N2200. Results show that all-PSCs based on the imine-substituted derivative PBDT-TTz exhibit power conversion efficiencies (PCE) as high as 8.4%, which largely outperform the analogue PBDT-TT-based ones with PCEs of only 0.7%. This work reveals that the imine substitution in polymer backbones of PBDT-TTz not only increases the ionization potential (IP) and electron affinity (EA), narrows the optical gap (Eopt), but also has significantly impacts on the BHJ film morphologies. PBDT-TTz:N2200 BHJ blends present better miscibility, suppressed phase separation, much stronger crystallinity, and face-on ordering, which are contributed to efficient exciton dissociation, charge transportation, and therefore, high-efficiency in all-PSCs. This study demonstrates that the imine-substituted polymers composed of TTz motif, which can be easily synthesized through a facile two-step procedure, are a promising class of wide bandgap polymer donors for efficient all-PSCs.
关键词： Imine substitution,All-polymer solar cells,Thiazolothiazole,Wide bandgap polymer donors,BHJ film morphologies
更新于2025-09-12 10:27:22
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Rationally pairing photoactive materials for high-performance polymer solar cells with efficiency of 16.53%
摘要： The emergence of non-fullerene acceptors (NFA) offers a promising opportunity to develop high-performance donor/acceptor pairs with high power conversion efficiency, as NFAs offer tunable energy levels, broad absorption and suitable aggregation property. In order to enhance light-harvesting capability of active layers, we choose a wide bandgap polymer PTQ10 as the donor to blend with a narrow bandgap NFA Y6 as the acceptor. In comparison with PTQ10:IDIC blend, ~130 nm red-shifted absorption spectrum is observed in the PTQ10:Y6 blend, which potentially enhance the short-circuit current density (Jsc) for the PSCs. In addition, the optimal PTQ10:Y6 blend shows higher photoluminescence quenching efficiency and more efficient charge separation, higher charge mobilities, as well as weaker bimolecular recombination over the PTQ10:IDIC blend, which leads to an outstanding power conversion efficiency (PCE) of 16.53%, with a notable Jsc of 26.65 mA cm?2 and fill factor (FF) of 0.751.
关键词： nonfullerene acceptor,power conversion efficiency,polymer donor,polymer solar cells
更新于2025-09-12 10:27:22
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Design of parallel-connected polymer tandem solar cells using efficient low bandgap PTB7-Th:PC71BM blend
摘要： Parallel-connected tandem cells adopting a highly efficient donor polymer, PTB7-Th, combined with acceptor fullerene PC71BM as the back sub-cell was introduced to further improve the performance of polymer solar cells. Design of the device architecture was investigated using modeling and simulation methods based on the transfer matrix formalism. To optimize the device structure, detailed analysis of the effect of active layer thickness, different device structure, and transparent Ag intermediated electrode on the short-circuit current density has been studied. It was found the long-wavelength absorption in the top-illuminated ITO-free back cell was significantly enhanced due to the resonant microcavity effect, leading to an efficient utilization of the incident light and increased photocurrent. Giving these advantages, the power conversion efficiency of the parallel homo-tandem cell was estimated to be ~ 11%, which was ~ 15% higher than that of a single cell of PTB7-Th. Moreover, the maximum achievable current density and the corresponding optimum active layer thickness of the sub-cells varied a little as the thickness of ultrathin Ag layer was changed, indicating that parallel connection architecture provided more freedom in the design and optimization for high-performance tandem solar cells.
关键词： PC71BM,Polymer solar cells,Microcavity effect,Transfer matrix formalism,PTB7-Th,Parallel-connected tandem cells
更新于2025-09-12 10:27:22
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Cyclopentadithiophene cored A-π-D-π-A non-fullerene electron acceptor in ternary polymer solar cells to extend the light absorption up to 900?nm
摘要： Conjugated small molecular non-fullerene electron acceptors (NFA) are considered as one of the critical materials for achieving high performance and low cost of polymer solar cells, and received much attention in the last few years. However, most of the NFAs are based on large fused π-aromatic core, which requires complicate synthesis efforts. In addition, the relatively weak light absorption limited to 800 nm of most the NAFs limits the energy harvesting capability of the solar cells. In this paper, we report an A-π-D-π-A type molecule cored with a cyclopentadithiophene unit, which can be easily synthesized in two steps from commercially available starting materials. This compound shows a broad absorption up to 900 nm in thin solid film, which is ascribed to the relatively high highest occupied molecular orbital (HOMO) energy level as confirmed by cyclic voltammery and theoratical calculation. Application of the compound in polymer solar cells was also investigated both in binary and in ternary systems. The optimized power conversion efficiency (PCE) in binary solar cell with PTB7-Th as donor is 5.76% with an open circuit voltage (VOC) of 0.838 V, a short circuit current (JSC) of 14.81 mA/cm2 and a fill factor (FF) of 46.4%. In the ternary solar cells which includes a second acceptor, PC71BM, the highest PCE achieved is 9.39% with a VOC of 0.803 V, a JSC of 19.01 mA/cm2, a FF of 61.6%, which is over 20% enhancement compared to the PTB7-Th:PC71BM system (PCE of 7.58%). This work develops a simple small molecule non-fullerene acceptor which can largely enhance the photo response in near infrared region to improve the performance of fullerene based organic solar cell.
关键词： Light absorption,Non-fullerene electron acceptor,Cyclopentadithiophene,Ternary systems,Polymer solar cells
更新于2025-09-12 10:27:22
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Construction of Effective Polymer Solar Cell Using 1,7-Disubstituted Perylene Diimide Derivatives as Electron Transport Layer
摘要： The poor compatibility of an inorganic electron transport layer with the active layer and an ultrathin film organic material becomes a great obstacle in producing high-quality polymer solar cells with high-throughput roll-to-roll (R2R) method. Novel effective polymer solar cells had been fabricated by introducing 1, 7-disubstituted perylene diimide derivatives PDIH, PDIC, and PDIN as an electron transporting layer. It was noteworthy that PDIN could obviously improve the power conversion efficiency of solar cells that incorporated a photoactive layer composed of poly[(3-hexylthiophene)-2, 5-diyl] (P3HT) and the fullerene acceptor [6, 6-phenyl-C71-butyric acid methyl ester] (PC71BM). The power conversion efficiency varies from 1.5% for ZnO transparent cathode-based solar cells to 2.1% for PDIN-based electron transport layer-free solar cells. This improved performance could be attributed to the following reasons: the interaction between N atom in PDIN and O atom in indium tin oxide (ITO) reduced the work function of ITO, increased the built-in electric field, and thus lowered the electron transport barrier and improved the electron extraction ability of cathode, the appropriate roughness of the active layer increased the contact area with anode interfacial layer and enhanced the hole transport efficiency. These experimental results revealed that PDIN can be a promising novel effective material with a simplified synthesis process and lower cost as an electron transporting layer.
关键词： polymer solar cells,electron transport layer,perylene diimide derivatives,indium tin oxide,power conversion efficiency
更新于2025-09-12 10:27:22
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Nonhalogenated-Solvent-Processed Efficient Polymer Solar Cells Enabled by Medium-Band-Gap A?π–D?π–A Small-Molecule Acceptors Based on a 6,12-Dihydro-diindolo[1,2- <i>b</i> :10,20- <i>e</i> ]pyrazine Unit
摘要： In this contribution, a series of A?π?D?π?A small molecules (SMs), IPY-T-IC, IPY-T-ICCl, and IPY-T-ICF, containing the central donor unit (D) of 6,12-dihydro-diindolo[1,2-b:10,20-e]pyrazine (IPY), the π-conjugated bridge of thiophene, and the end-accepting group (A) of 3-(dicyanomethylidene)indol-1-one, 5,6-dichloro-3-(dicyanomethylidene)indol-1-one, or 5,6-difluoro-3-(dicyanomethylene)indol-1-one, were developed, characterized, and employed as the acceptor materials for polymer solar cells (PSCs). Influences of the different end-accepting groups on thermal properties, spectral absorption, energy levels, photovoltaic performance, and film morphology of these small-molecule acceptors (SMAs) were investigated in detail. These SMAs exhibit an excellent thermal stability and strong crystallization. The absorption spectra of these SMs mainly locate the wavelength between 400 and 700 nm, associated with the optical band gaps in the range of 1.75?1.90 eV. Compared with nonhalogenated IPY-T-IC, the halogenated SMAs IPY-T-ICCl and IPY-T-ICF present better absorption abilities, wider absorption region, and downshifted highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels. With regard to the complementary spectral absorption and matched HOMO/LUMO levels, PTB7-Th as a low-band gap polymer was chosen to be an electron donor to pair with these SMAs for fabricating bulk-heterojuntion PSCs. Under optimized conditions, among these SMAs, the PTB7-Th:IPY-T-IC-based PSC processed from a halogenated solvent system (chlorobenzene + 1-chloronaphthalene) delivers the best power conversion efficiency (PCE) of 7.32%, mainly because of more complementary spectral absorption, upper-lying LUMO level, higher and balanced carrier mobility, more efficiently suppressed trap-assisted recombination, better charge collection property, and blend morphology. Encouragingly, an improved PCE of up to 7.68% is achieved when the IPY-T-IC-based solar cell was processed from a nonhalogenated solvent system (o-xylene + 2-methylnaphthalene). In view of the large band gap of these IPY-based SMAs, the PCE of over 7.5% is notable and attractive for the related community. Our study argues that the IPY moiety is a potential electron-donating building moiety to develop medium-band-gap high-performance A?π?D?π?A SMAs for nonhalogenated-solvent-processed photovoltaic devices.
关键词： A?π?D?π?A,polymer solar cells,small-molecule acceptors,6,12-dihydro-diindolo[1,2-b:10,20-e]pyrazine,photovoltaic performance
更新于2025-09-12 10:27:22
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Difluorobenzoxadiazole-based conjugated polymers for efficient non-fullerene polymer solar cells with low voltage loss
摘要： Two donor-acceptor (D-A) conjugated copolymers based on difluorobenzoxadiazole (ffBX) and oligothiophenes, i.e., PffBX-2T and PffBX-TT, were designed and synthesized for polymer solar cells (PSCs). Compared to the polymers based on difluorobenzothiadiazole (ffBT) units, the two ffBX-based polymers presented identical optical bandgaps (~1.62 eV), but lower highest occupied molecular orbital (HOMO) energy levels. Owing to the down-shifted HOMO levels, the PSCs based on PffBX-2T and PffBX-TT showed lower voltage loss, and the open-circuit voltage (Voc) was ~0.1 V higher than that of the devices with the ffBT-based polymer. As a result, higher photovoltaic performance was achieved for the devices based on the ffBX-based polymers. The power conversion efficiencies (PCEs) of the non-fullerene PSCs with PffBX-2T and PffBX-TT as the donor were 8.72% and 10.12%, respectively. The superior device performance of PffBX-TT resulted from the efficient exciton dissociation and charge transport as well as weak charge recombination, which could be ascribed to the favorable face-on packing of the conjugated backbones and the desired morphology in the blend film. Our study demonstrates that difluorobenzoxadiazole is a promising building block for constructing conjugated polymers for high-performance non-fullerene PSCs.
关键词： voltage loss,difluorobenzoxadiazole,alkylthiophene side chains,non-fullerene polymer solar cells
更新于2025-09-12 10:27:22
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New Conjugated Polymers Based on Dithieno[2,3‐e:3′,2′‐g]Isoindole‐7,9(8H)‐Dione Derivatives for Applications in Nonfullerene Polymer Solar Cells
摘要： We have designed two new wide bandgap A1-D1-A2-D1 conjugated polymers with same dithieno[2,3-e:3’,2’-g]isoindole-7,9(8H)-dione (DTID) acceptor (A1) and D1 (thiophene donor) and different A2 acceptor units i.e. benzothiadiazole (BT) and fluorinated benzothiadiazole (f-BT) denoted as P113 and P114 and investigated the effect of fluorination the benzothiadiazole acceptor unit on photovoltaic properties of polymer solar cells using non-fullerene acceptor. We found that the incorporation of fluorine atom into the benzothiadiazole acceptor unit increases the absorption coefficients and the relative dielectric constant. The increase in the photoluminescence quenching, reduction in charge recombination loss and improvement in the charge carrier life are observed for the P114. These all factors resulted in dramatically improved the power conversion efficiency of P114:ITIC-m based polymer solar cell to 10.42 % with small energy loss of 0.56 eV as compared to P113 counterpart (8.74 % with energy loss of 0.69 eV) under identical conditions. The low energy loss is beneficial to overcome the trade-off between open circuit voltage and short circuit current.
关键词： low energy loss,dielectric constant,Polymer solar cells,power conversion efficiency,fluorinated backbone
更新于2025-09-12 10:27:22